In such cold chamber die casting machines, the injection plunger thereof should be in precise axial alignment with the cold or shot chamber thereof or otherwise excessive wear may occur in the injection system and cause premature replacement of parts. The plunger tip and shot chamber are particularly subject to wear and scoring and such may create clearance therebetween through which metal may be spat back and out of the shot chamber. This can be a safety hazard, and particularly a fire hazard when easily ignitable metals such as magnesium are being injected, and such thus renders the machine unsafe. Replacement of the worn parts is costly and time consuming, and replacement of the plunger tip and shot chamber is particularly costly as such parts are made of expensive materials, Moreover, the machine must be idle during replacement of worn parts, and the machine may be out of service for a lengthy period of time if a needed replacement part is not on hand or available.
Machine operation also may be adversely affected when the plunger and shot chamber are out of alignment. Binding between the plunger and shot chamber may occur and cause injection pressure to vary from cycle to cycle to the extent that a defective casting may be formed. This may be disastrous to the die caster particularly if the defect is not readily apparent until machining or plating thereof. In any event, the machine may produce castings of inconsistent quality.
In advanced machine operation, computerized and programmable control systems are widely used. Such systems depend on feed-back from hydraulic pressure feed-back sensors coupled to the hydraulic injection system to control plunger operation. When the plunger and shot chamber are out of alignment, inconsistent and unreliable feed-back information may be supplied and foul up the control systems which are expensive and often finicky.
To align the plunger and shot chamber, it is known to use a sliding rod on the outside of the shot chamber and a dial indicator for making adjustments. To make these adjustments, an experienced mechanic is required and many adjustments may have to be made just to bring the plunger and shot chamber into approximate alignment.
A more sophisticated method and apparatus obtaining a more precise alignment employs a telescope or laser with a fixture inserted in the shot chamber. As the telescope or laser is fitted in the shot chamber, a right angle lens is required for viewing purposes or otherwise the technician must insert his head into the die area which is quite dangerous. In any event, this technique requires skilled technicians and the equipment is quite costly.